Reduction jack for spinal rod placement and method of use

Abstract

A reduction jack for placing a spinal rod within a rod channel of a bone fixation screw includes a mounting stem having a tubular body, a plurality of teeth disposed on the body, a pair of legs projecting from the body, and catches disposed on the legs for engaging the bone fixation screw. A reduction sleeve at least partially encircles the mounting stem. A gear assembly is mounted on the reduction sleeve and engages the teeth on the body such that manipulation of the gear assembly facilitates movement of the reduction sleeve along the mounting stem. A first pawl is pivotably mounted to the reduction sleeve and resiliently biased against the teeth on the body, the first pawl being pivotable between a first position where the first pawl engages the teeth on the body and a second position wherein the first pawl does not engage the teeth on the body.

What is claimed is: 
     
       1. A reduction jack for placing a spinal rod within a rod channel of a bone fixation screw, comprising:
 an elongated, tubular, mounting stem comprising:
 a tubular body; 
 a plurality of teeth disposed on the body; 
 a pair of legs attached to and projecting from the body, at least a portion of the legs being separated by two spaced apart rod channels; and 
 means disposed on the legs for engaging the bone fixation screw; 
 a reduction sleeve at least partially encircling the mounting stem, the reduction sleeve having a proximal end and an opposing distal end; and 
 a first pawl pivotably mounted to the reduction sleeve and resiliently biased against the teeth on the body, the first pawl being pivotable between a first position where the first pawl engages the teeth on the body and a second position wherein the first pawl does not engage the teeth on the body. 
 
 
     
     
       2. The reduction jack as recited in  claim 1 , further comprising a lever mounted on the reduction sleeve, the lever being movable between a first position where the first pawl engages the teeth on the body and a second position wherein the first pawl does not engage the teeth on the body. 
     
     
       3. The reduction jack as recited in  claim 2 , wherein the reduction sleeve can freely slide in either direction along the length of the mounting stem when the lever is in the second position. 
     
     
       4. The reduction jack as recited in  claim 1 , further comprising a second pawl pivotably mounted to the reduction sleeve and resiliently biased against the teeth on the body, the second pawl being offset from the first pawl so that the first and second pawl either simultaneously engage different teeth or simultaneously engage different sides of the same tooth. 
     
     
       5. The reduction jack as recited in  claim 4 , further comprising a lever mounted on the reduction sleeve, the lever being movable between a first position where the first pawl and second pawl engage the teeth on the body and a second position wherein the first pawl and second pawl do not engage the teeth on the body. 
     
     
       6. The reduction jack as recited in  claim 1 , wherein at least one of the legs of the mounting stem is hingedly coupled to the body. 
     
     
       7. The reduction jack as recited in  claim 6 , wherein the reduction sleeve can be moved between a first position which permits the at least one of the legs to outwardly pivot and a second position which prevents the at least one of the legs from outwardly pivoting. 
     
     
       8. The reduction jack as recited in  claim 1 , wherein the means for engaging the bone fixation screw comprises a catch inwardly projecting from an interior surface of each leg. 
     
     
       9. The reduction jack as recited in  claim 1 , further comprising a gear assembly, the gear assembly comprising:
 a first gear engaging the teeth on the body; 
 a second gear connected to the first gear; and 
 a driver socket formed on the second gear such that rotation of the drive socket facilitates rotation of the second gear which in turn rotates the first gear, the gears being configured to produce a mechanical advantage. 
 
     
     
       10. The reduction jack as recited in  claim 1 , further comprising an extension removably coupled to the mounting stem. 
     
     
       11. A spine fixation system comprising:
 a bone fixation screw having a rod channel formed thereon; 
 an elongated spinal rod received within the rod channel of the bone fixation screw; and 
 reduction jack comprising:
 an elongated, tubular, mounting stem comprising:
 a tubular body; 
 a plurality of teeth disposed on the body; and 
 a pair of legs attached to and projecting from the body and being removably coupled to the bone fixation screw; 
 a reduction sleeve at least partially encircling the tubular stem, the reduction sleeve having a proximal end and an opposing distal end, the distal end being biased against the spinal rod; and 
 a first pawl pivotably mounted to the reduction sleeve and resiliently biased against the teeth on the body, the first pawl being pivotable between a first position where the first pawl engages the teeth on the body and a second position wherein the first pawl does not engage the teeth on the body. 
 
 
 
     
     
       12. The spine fixation system as recited in  claim 11 , further comprising a lever mounted on the reduction sleeve, the lever being movable between a first position where the first pawl engages the teeth on the body and a second position wherein the first pawl does not engage the teeth on the body, wherein the reduction sleeve can freely slide in either direction along the length of the mounting stem when the lever is in the second position. 
     
     
       13. A method for operating a spinal reduction jack, the method comprising:
 coupling a distal end of a tubular mounting stem to a bone fixation screw having a rod channel formed thereon, the distal end of a tubular mounting stem having a pair of rod channels formed thereon in which a spinal rod is received; 
 moving a lever on a reduction sleeve that at least partially encircles the mounting stem to a second position so that a first pawl disengages from teeth on the mounting stem; 
 with the lever in the second position, freely sliding the reduction sleeve along a length of the mounting stem so that a distal end of the reduction sleeve is disposed against or adjacent to the spinal rod; 
 moving the lever to a first position so that the first pawl engages the teeth; and 
 manipulating the reduction sleeve so that the distal end of the reduction sleeve reduces the spinal rod into the rod channel of the bone fixation screw. 
 
     
     
       14. The method as recited in  claim 13 , further comprising passing the shaft of a driver down through the mounting stem and coupling a fastener on the shaft to the bone fixation screw so as to secure the spinal rod within the rod channel of the bone fixation screw. 
     
     
       15. The method as recited in  claim 13 , wherein moving the lever to the second position causes the first pawl and a second pawl to disengage from the teeth on the mounting stem. 
     
     
       16. The method as recited in  claim 13 , further comprising:
 moving the lever back to the second position after the spinal rod has been reduced into the rod channel; and 
 freely sliding the reduction sleeve on the mounting stem away from the spinal rod.